It is known to apply a VLF alternating voltage to an electrical system or component presenting a capacitive load, to carry out a so-called voltage stress test, proof test or withstand test of the integrity of the insulation of the component, as well as further types of testing. For example, such testing is applied to shielded cables, dielectric cables, or buried power cables, and especially medium voltage cables, among other test objects. Various different voltage source arrangements and switching arrangements are known for generating a VLF test voltage for testing cables. For example, the German Patent Publication DE 36 29 352 C1 discloses a switching arrangement for generating a cosine rectangular wave test voltage for such cable testing. This arrangement uses a rotating electromechanical switch for carrying out the switching function. An advantage of that arrangement is that, during the voltage polarity reversal or switchover, a load change rate du/dt comparable to the power main's frequency arises for the cable to be tested. On the other hand, disadvantages of that switching arrangement are that the rotating electromechanical switch is very subject to mechanical wear, that an asymmetrical cable loading arises because the polarity reversal or alternation losses are compensated only in the negative phase, and that an auxiliary high voltage backup or smoothing capacitor is necessary for low testing power levels.
Furthermore, the German Patent Publication DE 195 13 441 A discloses a switching arrangement which similarly demonstrates the generation of a VLF test voltage. Also, the German Patent Publications DE 37 00 647 A, DE 37 37 373 A and DE 38 05 733 A disclose other switching arrangements for generating test voltages for insulation testing of cables.
In the above known arrangements, a test voltage is used for generating sinusoidal voltages. However, due to the common functional or operating principle for carrying out the testing, it is disadvantageous in all of those arrangements, that the energy fed into the cable during charging in the first and third quadrants of one sinusoidal cycle of the voltage progression during the testing, must again be extracted from the test object i.e. the cable during the respective following discharge phases in the second and fourth quadrants of the given cycle of the m voltage progression. This discharged energy must then be converted into heat to be dissipated. As a result, such known arrangements suffer a relatively poor efficiency, which also limits the maximum testing power that can be realized.